AbstractNutritive value depends on the concentration of nutrients in the feed, the availability of these nutrients to the animal, the efficiency with which the absorbed nutrients are used by the animal, and the effect of feed composition on the voluntary intake of the feed. The following chapter, assesses the nutritive value of herbage and presents the factors that affect it: plant maturity, genetic variation, environmental factors (i.e., temperature and light), and grazing management. The estimation of nutritive value using the total collection trial as well as marker techniques is discussed. The chapter also elaborates on the use of database selection, the development and evaluation of prediction equations, chemical procedures, biological procedures (i.e., in vitro procedures using either rumen microorganisms or enzyme preparations, or using the in situ nylon-bag technique), and physical procedures (i.e., near-infrared reflectance spectroscopy, and tensile or shear strength) to predict the nutritive value of herbage.